1. Field of the Invention
This invention relates generally to the field of telecommunications and, more particularly, to wireless communications.
2. Description of the Related Art
Owners and/or operators of communication networks, i.e., the service providers, are constantly searching for methods and equipment that can meet the changing needs of their subscribers. Subscribers of communication networks, including wireless communication networks, require higher information throughput in order to exploit the expanding range of services being provided by current communication networks. For example, wireless communication subscribers are now able to have simultaneous access to data networks such as the Internet and to telephony networks such as the Public Switched Telephone Network (PSTN).
Speech transmission is the main service supported by the first and second-generation wireless communication systems. However, the demand for data services is ever-increasing. Data traffic, unlike voice traffic, tends to occur in bursts and is more delay tolerant. The amount of data that can be sent to a user is dependent on the amount of data that has arrived for transfer to the user. One technique for communicating data to users includes identifying the users with data packets ready for transmission, prioritizing the users in order by channel condition, and sending the data using the available channel resources.
Downlink traffic for different traffic rates is conveyed using a multiple rate combination of the basic rate. Traffic with rate m times the basic rate may be sent using m codes and the received signal power may be m times larger than the basic power allocated to the basic rates. However, in the case of a shared data and voice application, the total available power at the transmitter for data traffic varies due to various reasons such as overhead power allocation or dynamic changes in the voice user's power consumption. These variations could be very slow (e.g., in the order of hours) or could be fast varying (e.g., as function of the channel variation in the order of milliseconds). In addition, the total system available power at the transmitter may also change over time. Hence, an assumption of fixed power allocation for data service, for example, is not valid in these situations.
In Universal Mobile Telecommunications Systems (UMTS), users are code multiplexed using different orthogonal variable spreading factor (OVSF) codes and variable processing gain. Typically, the number of codes assigned to the users depends on the size of the data packet to be transferred, and the available transmit power is evenly divided amongst the total number of codes. Assigning the channelization codes and then dividing the available power amongst the codes does not optimize the capacity of the data channels. In the case where the total allocated codes for a user are assigned based on the user packet or buffer size, the total power assigned is thus proportional to the total number of assigned codes rather than optimized to the channel conditions. However, users with better channel conditions may not require the same power to meet a target error rate than a user with a more degraded channel.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.